1. Field of the Invention
This invention relates to a novel fluorine-containing surfactant and a process for producing the same.
2. Description of the Prior Art
Heretofore, as fluorine-containing surfactants, there have been known those prepared by use of perfluoroalkylsulfonyl fluoride (C.sub.8 F.sub.17 SO.sub.2 F), perfluoroalkylcarbonly fluoride (C.sub.7 F.sub.15 COF), etc. obtained by electrolytic fluorination as a starting material and by bonding a polyether group to these through an amide group or an ester group. However, in such reaction, there is involved the problem that the yield of perfluoroalkyl derivatives with 6 or more carbon atoms useful as surfactants is very low. Further, there is also the problem that esters of carboxylic acids having perfluoroalkyl groups (C.sub.7 F.sub.15 COOR) are susceptible to hydrolysis and unstable.
On the other hand, polyether surfactants obtained by the reaction of ethylene oxide with perfluoroalkylcarbinol have been well known in the art, but because the polymerization degree of ethylene oxide can be controlled with difficulty, it is not a satisfactory production process.
Accordingly, there has been developed a process which comprises allowing dimer to tetramer oligomers of hexafluoropropylene (HFP) to react with terminal hydroxy groups of polyether (see Japanese Patent Publication (KOKOKU) No. 1319/1984). However, HFP oligomers contain several kinds of isomers mixed therein, and since addition of hydroxyl groups of the polyether may not sometimes proceed depending on the structure of such isomers, there is the problem that the reaction efficiency is low.
Further, there has been proposed a process for producing a surfactant which comprises reacting an epoxide having a fluorine-containing organic group ##STR2## with a polyether having hydroxyl groups at terminal ends (see Japanese Pre-examination Patent Publication (KOKAI) No. 133244/1986), but in this case, in addition to the high cost of starting materials, the epoxy ring of the epoxide is unstable, and the process is not advantageous also from the viewpoint of reaction efficiency.